使用顶点缓冲区对象 (VBO) 渲染 Kinect 点云

Question

我正在尝试制作一个动态点云可视化工具。使用 Kinect 传感器每帧都会更新这些点。为了抓取我正在使用 OpenCV 和 GLUT 显示的帧。 OpenCV API 为点 xyz 位置返回 640 x 480 (float *)，为 rgb 颜色数据返回 640 x 480 (int *)。 为了获得最大的性能，我尝试在流模式下使用顶点缓冲区对象而不是简单的顶点数组。我能够用顶点数组渲染它，但我的 VBO 实现没有渲染任何东西。我在声明中尝试了一堆不同的命令，但我找不到我缺少的东西。有人可以尝试指出我正确的方向吗？这是简化的代码：（我已经按照Christian Rau的要求重写了错误的版本，所以你们可以理解我的错误）

int main()
{
    //Delaring variables, inittiating glut, setting camera and checking the compatibility as http://www.songho.ca/opengl/gl_vbo.html
    glutDisplayFunc(displayCB);
    glutIdleFunc(displayCB); 
    ... 
    //Inittiating the vertex buffers
    if(vboSupported)
    {
        glGenBuffers(1, &vertex_buffer);
        glBindBuffer(GL_ARRAY_BUFFER_ARB, buffer);
        glBufferData(GL_ARRAY_BUFFER_ARB, (sizeof(GLfloat) * 640 * 480 * 3), 0, GL_STREAM_DRAW_ARB);
        glBufferSubData(GL_ARRAY_BUFFER_ARB, 0,  (sizeof(float) * 640 * 480 * 3), point_cloud.points_position); 

        glGenBuffers(2, &color_buffer);
        glBindBuffer(GL_ARRAY_BUFFER_ARB, buffer);
        glBufferData(GL_ARRAY_BUFFER_ARB, (sizeof(GLbyte) * 640 * 480 * 3), 0, GL_STREAM_DRAW_ARB);
        glBufferSubData(GL_ARRAY_BUFFER_ARB, 0,  (sizeof(char) * 640 * 480 * 3), point_cloud.points_color); 
    }
    //glutMainLoop(), cleaning memory, ending main
    ..
}

//Updating the screen
void displayCB()
{
    point_cloud.update();

    // clear buffer
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

    // save the initial ModelView matrix before modifying ModelView matrix
    glPushMatrix();

        glBindBuffer(GL_ARRAY_BUFFER_ARB, color_buffer);
        glBufferSubData(GL_ARRAY_BUFFER_ARB, 0,  (sizeof(char) * 640 * 480 * 3), point_cloud.points_color); 
        glColorPointer(3, GL_UNSIGNED_BYTE, 0, 0);

        glBindBuffer(GL_ARRAY_BUFFER_ARB, vertex_buffer);
        glBufferSubData(GL_ARRAY_BUFFER_ARB, 0,  (sizeof(float) * 640 * 480 * 3), point_cloud.points_position); 
        glVertexPointer(3, GL_FLOAT, 0, 0));

        // enable vertex arrays
        glEnableClientState(GL_VERTEX_ARRAY);
        glEnableClientState(GL_COLOR_ARRAY);

        glDrawArrays(GL_POINT, 0, 640*480);

        glDisableClientState(GL_VERTEX_ARRAY);  // disable vertex arrays
        glDisableClientState(GL_COLOR_ARRAY);

        glBindBuffer(GL_ARRAY_BUFFER_ARB, 0);

    glPopMatrix();

    glutSwapBuffers();
}

Answer 1

PS：程序已启动并运行，但与 Vertex Array 版本相比，我看不到平均性能有任何改进。这样好吗？ 问题已解决。我做了三处改动：

1 - I though that glGenBuffers first parameter was the number that
would be associated to the buffer, instead, its the number of
buffers that would be allocated. This doesn't matter anyway, because
now I'm using a single buffer and adding all the data to it. Didn't
solved the problem, but was going in the right way.

2 - There are two ways of being able to use OpenGL VBO functions.
First, you can bind the ARB  version functions by yourself OR you
can add glew.h and use glewInit() after starting an OpenGL context.
The second option is a LOT cleaner and I changed my code so I don't
use the ARB versions anymore. Still didn't solved the problem.

3 - Christian Rau asked me for glErrors in the code, so, I wrote it
after each OpenGL operation in displayCB. After glDrawArrays I got
an 0x00500 error, that means there is an invalid enum, so I noticed
I was using GL_POINT as parameter to glDrawArrays, instead of
GL_POINTS, so silly that makes me want to kill myself.

最终代码：

//EDIT: Added glew.h as a header and I´m not using the ARB version anymore
#include <glew.h>

    int main()
    {
        //Declaring variables, initiating glut, setting camera and checking the compatibility as http://www.songho.ca/opengl/gl_vbo.html
        glutDisplayFunc(displayCB);
        glutIdleFunc(displayCB); 
        ...

        //EDIT: IS VERY IMPORTANT TO ADD IT AS SOON AS YOU START AN OPENGL CONTEXT.
        initGlew();

        //Inittiating the vertex buffers
        if(vboSupported)
        {
           //EDIT: I was using two buffers, one for color and another for the vertex. I changed the code so I use  a single buffer now.
           //EDIT: Notice that I'm not using the ARB version of the functions anymore.
            glGenBuffers(1, &buffer);
            glBindBuffer(GL_ARRAY_BUFFER_ARB, buffer);
            glBufferData(GL_ARRAY_BUFFER_ARB, (sizeof(GLfloat) * 640 * 480 * 3) + (sizeof(GLbyte) * 640 * 480 * 3), 0, GL_STREAM_DRAW_ARB);
        }
        //glutMainLoop(), cleaning memory, ending main
        ..
    }

    //Updating the screen
    void displayCB()
    {
        point_cloud.update();

        // clear buffer
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

        // save the initial ModelView matrix before modifying ModelView matrix
        glPushMatrix();

            glBindBuffer(GL_ARRAY_BUFFER_ARB, buffer);
            glBufferSubData(GL_ARRAY_BUFFER_ARB, 0,  (sizeof(char) * 640 * 480 * 3), point_cloud.points_color); 
            glBufferSubData(GL_ARRAY_BUFFER_ARB, (sizeof(char) * 640 * 480 * 3), (sizeof(float) * 640 * 480 * 3), point_cloud.points_position);

            // enable vertex arrays
            glEnableClientState(GL_VERTEX_ARRAY);
            glEnableClientState(GL_COLOR_ARRAY);

            glColorPointer(3, GL_UNSIGNED_BYTE, 0, 0);
            //EDIT: Added the right offset at the vertex pointer position
            glVertexPointer(3, GL_FLOAT, 0, (void*)(sizeof(char) * 640 * 480 * 3));

            //EDIT: Was using GL_POINT instead of GL_POINTS
            glDrawArrays(GL_POINTS, 0, 640*480);

            glDisableClientState(GL_VERTEX_ARRAY);  // disable vertex arrays
            glDisableClientState(GL_COLOR_ARRAY);

            glBindBuffer(GL_ARRAY_BUFFER_ARB, 0);

        glPopMatrix();

        glutSwapBuffers();
    }